Double-curved-surface non-uniform wetting micro-nano structure for strengthening boiling / evaporation heat transfer and manufacturing method and application of double-curved-surface non-uniform wetting micro-nano structure

Abstract

The invention discloses a double-curved-surface non-uniform wetting micro-nano structure for strengthening boiling / evaporation heat transfer and a manufacturing method and application, and belongs to the technical field of heat transfer. The structure comprises a substrate and a double-curved-surface three-dimensional super-hydrophilic micro-nano structure array; the substrate has hydrophobicity / super-hydrophobicity; the array is composed of a plurality of upwards-convex hyperboloid three-dimensional super-hydrophilic micro-nano structures. The hyperboloid three-dimensional super-hydrophilic micro-nano structure comprises a convex main body and a top concave cavity; and the side wall of the convex main body and the inner wall of the concave cavity at the top are curved surface structures and are full of super-hydrophilic micro-nano porous structures. The transverse growth space of bubbles generated by boiling is restrained, expansion and combination of the bubbles generated by boiling are restrained, nucleation and separation of the bubbles in a super-hydrophobic area are promoted, the water storage capacity can be increased through a top catenary face, boiling / evaporation liquid supply is enhanced, capillary liquid supply is promoted, and the heat transfer coefficient is increased through combination of a hyperboloid mixed super-wetting three-dimensional structure; and the heat transfer limit is improved by means of the double-curved-surface three-dimensional curved surface pinning effect under the ultrahigh superheat degree by adhering liquid film boiling.

Description

Technical Field

[0001] The present invention belongs to the field of heat transfer technology, and relates to a heat transfer structure, and in particular to a hyperbolic non-uniform wetting micro-nano structure for enhancing boiling / evaporation heat transfer, a manufacturing method, and an application thereof. Background Art

[0002] In the future, electronic devices, new energy and aerospace equipment will develop towards extreme service environments, extreme integration and extreme performance. Thermal power consumption and heat flux density will continue to rise, and heat dissipation problems will become a bottleneck restricting their development. Studies have shown that the failure rate of electronic systems caused by increased heat flux density has reached more than 55%, and the failure rate will double for every 10°C increase in temperature (Applied Energy. 2018; 223: 383-400); high power density and lightweight fuel cell systems have great application value in space exploration, new energy vehicles and aircraft, but excessive or uneven temperatures lead to reduced plate / exchange membrane loss life, which is an important factor hindering its development. Therefore, the development of high-performance radiators has become the key to promoting the development of advanced systems. Boiling phase change heat transfer can fully utilize the latent heat of liquid working fluid to transfer a large amount of heat under relatively small overheating conditions. The heat transfer coefficient is two orders of magnitude larger than that of liquid convection, and it is an ideal thermal management technology for high heat flux equipment. The boiling heat transfer rate is characterized by the heat transfer coefficient, and the heat transfer limit is measured by the critical heat flux. Ideal boiling heat transfer requires both high heat transfer coefficient and high critical heat flux (International Journal of Heat and Mass Transfer. 2020; 161: 120265; Journal of Heat Transfer. 1968; 90(2): 231-8). Among them, high heat transfer coefficient can be achieved by hydrophobic surface (the bubble nucleation energy barrier on hydrophobic surface is 2-3 orders of magnitude smaller than that on hydrophilic surface, and the surface is easier to nucleate boiling, with high heat transfer coefficient, but the weak capillary force on the hydrophobic surface cannot ensure sufficient liquid supply in the boiling zone, so the critical heat flux is low (Applied Thermal Engineering. 2019; 163: 114358)). High critical heat flux can be obtained through hydrophilic surfaces (although the hydrophilic surface has a large bubble nucleation energy barrier and a low heat transfer coefficient, its strong capillary force can achieve sufficient liquid supply, so a high critical heat flux can be obtained (Applied Thermal Engineering.2023;225:120158;International Journal of Heat and Mass Transfer.2020;147:118956)). It is difficult to meet the hydrophobic demand for improving the heat transfer coefficient and the hydrophilic demand for improving the heat transfer limit (critical heat flux) at the same time. Although the use of mixed wetting surfaces can significantly improve the heat transfer coefficient or critical heat flux, one performance indicator must be sacrificed. It can be seen that how to simultaneously improve the heat transfer coefficient and the heat transfer limit has become a bottleneck problem restricting the development of boiling heat transfer technology. Summary of the invention

[0003] The present invention provides a hyperbolic non-uniform wetting micro-nano structure for enhancing boiling / evaporation heat transfer, a manufacturing method and an application thereof, so as to overcome the defects of the prior art.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] In the first aspect, the present invention provides a hyperbolic non-uniform wetting micro-nano structure for enhancing boiling / evaporation heat transfer, including a substrate and a hyperbolic three-dimensional super-hydrophilic micro-nano structure array on the substrate surface; the substrate has hydrophobic / super-hydrophobic properties; the hyperbolic three-dimensional super-hydrophilic micro-nano structure array is composed of a number of hyperbolic three-dimensional super-hydrophilic micro-nano structures that are convex on the top (i.e., wide on the top and narrow on the bottom); the hyperbolic three-dimensional super-hydrophilic micro-nano structure includes a convex body and a top concave cavity; the side walls of the convex body and the inner walls of the top concave cavity are both curved and are covered with super-hydrophilic micro-nano porous structures.

[0006] Optionally, the cross-sectional profiles of the convex body side wall and the top concave cavity inner wall are both catenaries.

[0007] Optionally, the hyperbolic three-dimensional super-hydrophilic micro-nano structure is a columnar body of revolution, and a plurality of bodies of revolution are orthogonally arranged to form a hyperbolic three-dimensional super-hydrophilic micro-nano structure array.

[0008] Optionally, the convex body of the hyperbolic three-dimensional super-hydrophilic micro-nano structure has a bottom diameter of 0.1 to 1.0 mm, a top diameter of 0.2 to 5.0 mm, a height of 0.1 to 5.0 mm, and a top diameter to height ratio greater than 1; the depth of the top cavity is 0.1 to 3.0 mm; and the spacing between the hyperbolic three-dimensional super-hydrophilic micro-nano structures is 0.4 to 10 mm.

[0009] Optionally, the hyperbolic three-dimensional super-hydrophilic micro-nano structure is a strip-shaped stretching body that crosses the substrate, and a plurality of stretching bodies are arranged in parallel to form a hyperbolic three-dimensional super-hydrophilic micro-nano structure array.

[0010] Optionally, the convex body of the hyperbolic three-dimensional super-hydrophilic micro-nano structure has a bottom width of 0.1 to 1.0 mm, a top width of 0.2 to 5.0 mm, a height of 0.1 to 5.0 mm, and a top width-to-height ratio greater than 1; the depth of the top cavity is 0.1 to 3.0 mm; and the spacing between the hyperbolic three-dimensional super-hydrophilic micro-nano structures is 0.4 to 10 mm.

[0011] Optionally, the substrate is a smooth surface or a surface having a micro-nano structure.

[0012] Optionally, the material of the substrate is diamond or metals such as copper and nickel, and the material of the hyperbolic three-dimensional super-hydrophilic micro-nano structure is metals such as copper and nickel.

[0013] In a second aspect, the present invention provides a method for manufacturing the above-mentioned hyperbolic non-uniform wetting micro-nano structure for enhancing boiling / evaporation heat transfer, comprising the following steps: step one, performing CVD chemical vapor deposition on a diamond or metal surface to obtain hydrophobicity / super-hydrophobicity to obtain a substrate; step two, using nanosecond, picosecond or femtosecond pulsed lasers to process micropores or striped slit arrays that penetrate the upper and lower surfaces of the diamond-processed substrate surface, or processing hydrophilic micropores, micropits, striped slits or striped groove arrays on the metal-processed substrate surface, wherein the micropores and striped slits penetrate the upper and lower surfaces, and the micropits and striped grooves do not penetrate the upper and lower surfaces; using a metal plate as an anode, processing a hydrophilic micropore / pit or striped groove array; A metal substrate with a slit / groove array is used as a cathode, or an aluminum metal film is attached to the back of a diamond substrate with a hydrophilic micropore or stripe slit array as a cathode; the cathode is contacted with the electroplating solution and pulled upward to construct a liquid bridge for constant potential electrodeposition; the liquid bridge constructed by the micropores / pits is a rotating body, and a convex body of the rotating body is obtained by electrodeposition; the liquid bridge constructed by the stripe slit / groove is a stretched body, and a convex body of the stretched body is obtained by electrodeposition; a nanosecond, picosecond or femtosecond pulse laser is used to secondary process a top concave cavity on the top of the convex body to obtain a hyperbolic three-dimensional super-hydrophilic micro-nano structure; step three, chemical or electrochemical etching is used to process a super-hydrophilic micro-nano porous structure on the surface of the hyperbolic three-dimensional super-hydrophilic micro-nano structure.

[0014] In a third aspect, the present invention provides the application of the above-mentioned hyperbolic non-uniform wetting micro-nano structure for enhancing boiling / evaporation heat transfer in heat transfer.

[0015] The present invention combines surface superwettability and three-dimensional micro-nano configuration design, and proposes a method for enhancing boiling heat transfer using a hyperbolic hybrid superwettability micro-nano structure surface: using a hydrophobic / superhydrophobic substrate to promote nucleation to improve the heat transfer coefficient, constructing a hyperbolic three-dimensional superhydrophilic micro-nano structure to inhibit bubble expansion and merging to achieve continuous boiling; at the same time, using the pinning effect of the hyperbolic three-dimensional surface to adhere to the liquid film boiling under ultra-high superheat to improve the heat transfer limit. In addition, this type of structural surface that combines hybrid superwettability with complex three-dimensional micro-nano configurations is difficult to obtain by existing processing, so the invention also aims to explore the manufacturing method of this type of complex three-dimensional hybrid superwettability micro-nano structure surface, laying a scientific and technological foundation for the development of high-performance phase change heat sinks and the promotion of high heat flux density systems such as microelectronics, fuel cells, and phased array radars.

[0016] The beneficial effects of the present invention are:

[0017] 1. The present invention constructs a hyperbolic three-dimensional super-hydrophilic micro-nano structure array on a hydrophobic / super-hydrophobic substrate, which can use the hydrophobic / super-hydrophobic substrate to promote phase change nucleation. At the same time, the hyperbolic three-dimensional super-hydrophilic micro-nano structure array can constrain the lateral growth space of boiling bubbles, promote bubble detachment, and avoid the formation of air film, thereby greatly improving the boiling / evaporation phase change heat transfer limit.

[0018] 2. The hyperbolic three-dimensional super-hydrophilic micro-nano structure of the present invention is a structure that is narrow at the bottom and wide at the top, which can extend the super-hydrophilic micro-nano structure in the three-dimensional space above the surface to obtain a sufficient volume share, thereby maximizing the proportion of the hydrophobic area of ​​the hydrophobic / super-hydrophobic substrate while ensuring sufficient capillary liquid supply, thereby increasing the nucleation density of the hydrophobic area and improving the heat transfer coefficient.

[0019] 3. The side walls and inner walls of the hyperbolic three-dimensional super-hydrophilic micro-nano structure of the present invention are both curved. When heat flux is transferred, the curved surface will pin the attached liquid film to achieve liquid film evaporation / boiling with an ultra-high heat transfer coefficient. The hyperbolic design greatly increases the liquid film pinning area, further improving the evaporation and boiling heat transfer performance.

[0020] 4. The surface of the hyperbolic three-dimensional super-hydrophilic micro-nano structure of the present invention has a super-hydrophilic micro-nano porous structure, in which the nanostructure is an ideal nucleation site at high heat flux, which can promote phase transformation nucleation at high heat flux input and improve the heat transfer efficiency when approaching the heat transfer limit.

[0021] 5. The hyperbolic three-dimensional super-hydrophilic micro-nano structure of the present invention has a structural gradient from top to bottom, which can generate additional Laplace capillary pressure, improve the transmission efficiency of liquid from top to bottom, accelerate liquid supply, and achieve continuous and efficient boiling / evaporation heat transfer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of the hyperbolic non-uniform wetting micro-nano structure of Example 1;

[0023] Figure 2 is a cross-sectional view of the hyperbolic non-uniform wetting micro-nanostructure of Example 1;

[0024] Figure 3 This is a photo of the rotating body of the hyperbolic non-uniform wetting micro-nano structure of Example 1;

[0025] Figure 4 It is a schematic diagram of bubble nucleation and detachment of hyperbolic non-uniform wetting micro-nanostructure under low superheat, where a is bubble nucleation on hydrophobic / super-hydrophobic substrate under low surface superheat, b is bubble detachment from hydrophobic / super-hydrophobic substrate under low surface superheat, and c is bubble aggregation on hydrophobic / super-hydrophobic substrate under low surface superheat;

[0026] Figure 5 This is a schematic diagram of the principle of the hyperbolic non-uniform wetting micro-nanostructure inhibiting bubble expansion and merging and rapid detachment under high superheat, where d is the nucleation and aggregation of bubbles on the hydrophobic / super-hydrophobic substrate under high surface superheat, e is the bubble detachment from the structure surface under high surface superheat, and f is the hyperbolic three-dimensional super-hydrophilic micro-nanostructure inhibiting bubble merging under high surface superheat;

[0027] Figure 6This is the principle diagram of hyperbolic pinning attached liquid film boiling of hyperbolic non-uniform wetting micro-nanostructure under ultra-high superheat, where g is the hyperbolic pinning attached liquid film under ultra-high surface superheat, and h is the hyperbolic surface liquid film boiling under ultra-high surface superheat. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with specific embodiments and drawings.

[0029] Example 1

[0030] like Figure 1 and Figure 2 As shown, this embodiment provides a hyperbolic non-uniform wetting micro-nano structure for enhancing boiling / evaporation heat transfer, including a substrate 1 and a hyperbolic three-dimensional super-hydrophilic micro-nano structure array 2 on its surface.

[0031] The substrate 1 is a smooth diamond surface with hydrophobicity.

[0032] The hyperbolic three-dimensional super-hydrophilic micro-nano structure array 2 is composed of a plurality of convex hyperbolic three-dimensional super-hydrophilic micro-nano structures 21. The hyperbolic three-dimensional super-hydrophilic micro-nano structure 21 is a columnar body of revolution, such as Figure 3 As shown, a plurality of rotating bodies are arranged orthogonally to form a hyperbolic three-dimensional super-hydrophilic micro-nano structure array 2. The hyperbolic three-dimensional super-hydrophilic micro-nano structure 21 includes a convex body 211 and a top concave cavity 212. The cross-sectional profiles of the side wall of the convex body 211 and the inner wall of the top concave cavity 212 are both catenary lines, and are covered with super-hydrophilic micro-nano porous structures. The actual image of the curved three-dimensional super-hydrophilic micro-nano structure 21 is shown in FIG. Figure 3 shown.

[0033] The bottom diameter of the convex body 211 is 0.5 mm, the top diameter is 1.5 mm, and the height is 1.0 mm; the depth of the top cavity 212 is 0.5 mm; and the spacing between the hyperbolic three-dimensional super-hydrophilic micro-nano structures 2 is 2.5 mm.

[0034] The method for manufacturing a hyperbolic non-uniform wetting micro-nano structure comprises the following steps:

[0035] Step 1: Perform CVD chemical vapor deposition on the surface of a diamond sheet to obtain hydrophobicity and obtain a substrate.

[0036] Step 2: Use nanosecond pulse laser to process a microhole array on the surface of the substrate.

[0037] A phosphor copper plate was used as the anode, and a 0.5 mm thick aluminum film was attached to the back of a substrate with a micropore array as the cathode. The cathode was contacted with the electroplating solution and pulled upward to construct a liquid bridge, and constant potential electrodeposition was performed to obtain a convex body of the rotating body.

[0038] A nanosecond pulse laser is used to secondary process a top concave cavity on the top of the convex body to obtain a hyperbolic three-dimensional super-hydrophilic micro-nano structure.

[0039] Step 3: Use chemical etching to process a super-hydrophilic micro-nano porous structure on the surface of the hyperbolic three-dimensional super-hydrophilic micro-nano structure.

[0040] like Figures 4 to 6 As shown in the figure, the hyperbolic non-uniform wetting micro-nanostructure comprehensively optimizes the three processes of enhancing boiling heat transfer: the hyperbolic three-dimensional super-hydrophilic micro-nanostructure can constrain the lateral growth space of bubbles generated by the hydrophobic / super-hydrophobic substrate, and increase the hyperbolic super-hydrophilic structure on the premise of expanding the proportion of the super-hydrophobic area, so as to achieve a mixed surface to improve the heat transfer effect. In addition, the hyperbolic three-dimensional super-hydrophilic micro-nanostructure can inhibit the merging of bubbles when they are too large, and the catenary-like surface on the top can also increase the water storage capacity and enhance the liquid supply capacity, thereby greatly improving the heat transfer limit, and can pin the liquid film under extremely high surface superheat to achieve liquid film boiling, further improving the heat transfer limit.

[0041] Example 2

[0042] The present embodiment provides a hyperbolic non-uniform wetting micro-nano structure for enhancing boiling / evaporation heat transfer, including a substrate and a hyperbolic three-dimensional super-hydrophilic micro-nano structure array on its surface.

[0043] The substrate is a super-hydrophobic copper surface with micro-nano structure.

[0044] The hyperbolic three-dimensional super-hydrophilic micro-nano structure array is composed of a number of convex hyperbolic three-dimensional super-hydrophilic micro-nano structures. The hyperbolic three-dimensional super-hydrophilic micro-nano structure is a strip-shaped stretching body that crosses the substrate, and a number of stretching bodies are arranged in parallel to form a hyperbolic three-dimensional super-hydrophilic micro-nano structure array. The hyperbolic three-dimensional super-hydrophilic micro-nano structure includes a convex body and a top concave cavity. The cross-sectional profiles of the side wall of the convex body and the inner wall of the top concave cavity are both catenaries, and are covered with super-hydrophilic micro-nano porous structures.

[0045] The bottom width of the convex body is 1.0 mm, the top width is 3.5 mm, and the height is 2.5 mm; the depth of the top cavity is 1.5 mm; and the spacing between the hyperbolic three-dimensional super-hydrophilic micro-nano structures is 5.0 mm.

[0046] The method for manufacturing a hyperbolic non-uniform wetting micro-nano structure comprises the following steps:

[0047] Step 1: Perform CVD chemical vapor deposition on the surface of a copper material having a micro-nano structure to obtain super-hydrophobicity, thereby obtaining a substrate.

[0048] Step 2: Use femtosecond pulse laser to process a hydrophilic stripe array on the surface of the substrate.

[0049] A phosphor copper plate is used as an anode, and a substrate with a hydrophilic stripe array is used as a cathode. The cathode is contacted with the electroplating solution and pulled upward to construct a liquid bridge, and constant potential electrodeposition is performed to obtain a convex main body of the stretched body.

[0050] A femtosecond pulse laser is used to secondary process a top concave cavity on the top of the convex body to obtain a hyperbolic three-dimensional super-hydrophilic micro-nano structure.

[0051] Step three: Use electrochemical etching to process a super-hydrophilic micro-nano porous structure on the surface of the hyperbolic three-dimensional super-hydrophilic micro-nano structure.

[0052] In the present invention, unless otherwise specified, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. In addition, the reagents, materials and operating procedures used herein are reagents, materials and conventional procedures widely used in the corresponding fields.

[0053] It should be noted that the terms such as "upper", "lower", "left", "right", "front", "back", etc. cited in the invention are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments in their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0054] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A hyperbolic non-uniform wetting micro-nanostructure for enhancing boiling / evaporation heat transfer, characterized in that: A hyperbolic three-dimensional super-hydrophilic micro-nanostructure array including a substrate and a substrate surface; The substrate is hydrophobic / superhydrophobic; The hyperbolic three-dimensional super-hydrophilic micro-nano structure array is composed of a number of upward convex hyperbolic three-dimensional super-hydrophilic micro-nano structures; the hyperbolic three-dimensional super-hydrophilic micro-nano structure includes a convex body and a top concave cavity; the side wall of the convex body and the inner wall of the top concave cavity are both curved and covered with super-hydrophilic micro-nano porous structures.

2. The hyperbolic non-uniform wetting micro-nanostructure for enhancing boiling / evaporation heat transfer according to claim 1, characterized in that: The cross-sectional profiles of the side wall of the convex body and the inner wall of the top concave cavity are both catenaries.

3. The hyperbolic non-uniform wetting micro-nano structure for enhancing boiling / evaporation heat transfer according to claim 1, characterized in that: The hyperbolic three-dimensional super-hydrophilic micro-nano structure is a columnar body of revolution, and a plurality of bodies of revolution are orthogonally arranged to form a hyperbolic three-dimensional super-hydrophilic micro-nano structure array.

4. The hyperbolic non-uniform wetting micro-nanostructure for enhancing boiling / evaporation heat transfer according to claim 3, characterized in that: The convex body of the hyperbolic three-dimensional super-hydrophilic micro-nano structure has a bottom diameter of 0.1 to 1.0 mm, a top diameter of 0.2 to 5.0 mm, a height of 0.1 to 5.0 mm, and a top diameter-to-height ratio greater than 1; the depth of the top cavity is 0.1 to 3.0 mm; and the spacing between the hyperbolic three-dimensional super-hydrophilic micro-nano structures is 0.4 to 10 mm.

5. The hyperbolic non-uniform wetting micro-nano structure for enhancing boiling / evaporation heat transfer according to claim 1, characterized in that: The hyperbolic three-dimensional super-hydrophilic micro-nano structure is a strip-shaped stretching body, and a plurality of stretching bodies are arranged in parallel to form a hyperbolic three-dimensional super-hydrophilic micro-nano structure array.

6. The hyperbolic non-uniform wetting micro-nanostructure for enhancing boiling / evaporation heat transfer according to claim 5, characterized in that: The convex body of the hyperbolic three-dimensional super-hydrophilic micro-nano structure has a bottom width of 0.1 to 1.0 mm, a top width of 0.2 to 5.0 mm, a height of 0.1 to 5.0 mm, and a top width-to-height ratio greater than 1; the depth of the top cavity is 0.1 to 3.0 mm; and the spacing between the hyperbolic three-dimensional super-hydrophilic micro-nano structures is 0.4 to 10 mm.

7. The hyperbolic non-uniform wetting micro-nanostructure for enhancing boiling / evaporation heat transfer according to claim 1, characterized in that: The substrate is a smooth surface or a surface having a micro-nano structure.

8. The hyperbolic non-uniform wetting micro-nanostructure for enhancing boiling / evaporation heat transfer according to claim 1, characterized in that: The material of the substrate is diamond or metal, and the material of the hyperbolic three-dimensional super-hydrophilic micro-nano structure is metal.

9. The method for manufacturing a hyperbolic non-uniform wetting micro-nano structure for enhancing boiling / evaporation heat transfer according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: Perform CVD chemical vapor deposition on a diamond or metal surface to obtain hydrophobicity / super-hydrophobicity to obtain a substrate; Step 2: Use nanosecond, picosecond or femtosecond pulsed laser to process micropores or stripe slit arrays on the surface of a diamond-processed substrate, or process hydrophilic micropores / pits or stripe slit / groove arrays on the surface of a metal-processed substrate; A metal plate is used as an anode and a metal substrate is used as a cathode, or an aluminum metal film is attached to the back of a diamond substrate as a cathode; the cathode is contacted with the electroplating solution and pulled upward to construct a liquid bridge, and constant potential electrodeposition is performed; the liquid bridge constructed by micropores / pits is a rotating body, and a convex body of the rotating body is obtained by electrodeposition; the liquid bridge constructed by stripe slits / grooves is a stretched body, and a convex body of the stretched body is obtained by electrodeposition; A top concave cavity is secondary processed on the top of the convex body by using nanosecond, picosecond or femtosecond pulse laser to obtain a hyperbolic three-dimensional super-hydrophilic micro-nanostructure; Step 3: Processing a super-hydrophilic micro-nano porous structure on the surface of the hyperbolic three-dimensional super-hydrophilic micro-nano structure by chemical or electrochemical etching.

10. Application of the hyperbolic non-uniform wetting micro-nano structure for enhancing boiling / evaporation heat transfer as claimed in any one of claims 1 to 8 in heat transfer.

Images